Toxic chemicals can cause genetic damage. The genetic material of a cell consists of genes, which exist in chromosomes. Genes and chromosomes contain the information that tells the cell how to function and how to reproduce (form new cells).
Some chemicals may change or damage the genes or chromosomes. This kind of change, or damage in a cell is called a mutation. Anything that causes a mutation is called a mutagen. Mutations may affect the way the cell functions or reproduces. The mutations can also be passed on to new cells that are formed from the damaged cell. This can lead to groups of cells that do not function or reproduce the same way the original cell did before the mutation occurred.
Some kinds of mutation result in cancer. Most chemicals that cause cancer also cause mutations. However, not all chemicals that cause mutations cause cancer.
Tests for the ability of a chemical to cause a mutation take little time and are relatively easy to perform. If testing shows a chemical to be a mutagen, additional testing must be done to determine whether or not the chemical also causes cancer.
Exposure to chemical substances may affect your children or your ability to have children. Toxic reproductive effects include the inability to conceive children (infertility or sterility), lowered sex drive, menstrual disturbances, spontaneous abortions (miscarriages), stillbirths, and defects in children that are apparent at birth or later in the child?s development.
Teratogens are chemicals which cause malformations or birth defects by directly damaging tissues in the fetus developing in the mother?s womb. Other chemicals that harm the fetus are called fetotoxins. If a chemical causes health problems in the pregnant woman herself, the fetus may also be affected. Certain chemicals can damage the male reproductive system, resulting in sterility, infertility, or abnormal sperm.
There is not enough information on the reproductive toxicity of most chemicals. Most chemicals have not been tested for reproductive effects in animals. It is difficult to predict risk in humans using animal data. There may be ?safe? levels of exposure to chemicals that affect the reproductive system. However, trying to determine a ?safe? level is very difficult, if not impossible. It is even more difficult to study reproductive effects in humans than it is to study cancer. At this time, only a few industrial chemicals are known to cause birth defects or other reproductive effects in humans.
CHROMOSOMAL ABBERATION
INTRODUCTION
Chromosomes are the organized form of DNA found in cells. Chromosomes contain one very long, continuous piece of DNA, which contains many genes, regulatory elements and other intervening nucleotide sequences. A broader definition of "chromosome" also includes the DNA-bound proteins which serve to package and manage the DNA. The word chromosome comes from the Greek (chroma, color) and (soma, body) due to their property of being stained very strongly with vital and supravital dyes. 2,3
chromosome abnormality reflects an abnormality of chromosome number or structure. Chromosome abnormalities usually occur when there is an error in cell division following meiosis or mitosis. There are many types of chromosome abnormalities.
Visible changes to chromosome structure and morphology have played a very important part as indicators of genetic damage in both clinical and cancer studies.Most of the changes encountered in clinical studies are ?secondary? or ?derived? aberrations. This is true also in cancer studies, except that here, there is an ongoing production of aberrations, so that in some cells, a mixture of primary and secondary changes is present, and a continuously changing karyotype (true chromosomal instability).To appreciate these observed secondary changes we need to understand the primary changes from which they are derive.4
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